I built a fairly large ported sub. It is a well braced 6 cu ft cab with twin 4" ports tuned to 24 Hz. I modeled it in WinISD to match the 15" driver. It came out great. Test tones come out silky smooth, unlike smaller speakers when trying to play low.
Problem is, I can't really hear the low notes. Around 18Hz, I can feel the walls flex and have a sensation in my ears. I know hearing gets much weaker at these low frequencies, but I'm wondering if the flexing of the stud walls is absorbing a lot of the sound?
Problem is, I can't really hear the low notes. Around 18Hz, I can feel the walls flex and have a sensation in my ears. I know hearing gets much weaker at these low frequencies, but I'm wondering if the flexing of the stud walls is absorbing a lot of the sound?
Yah, what he said. You can't hear 18 Hz. You can feel the pressure effects at higher SPLs. The fact that you can't hear anything means that you have a pretty low distortion sub - usually if you hear much of anything, you are "hearing" the distortion products, which occur at higher frequencies and thus are audible.
But what you say does have some truth to it - you can actually flex the sheetrock in your home at really low frequencies and this absorbs some energy. But it's a rather expensive proposal to try and fix that problem.
Finally, keep in mind that, depending on the alignment, accuracy of your tuning, etc., the output may be falling off and be -6dB already at 18 Hz, since this is below the tuning frequency.
-Charlie
But what you say does have some truth to it - you can actually flex the sheetrock in your home at really low frequencies and this absorbs some energy. But it's a rather expensive proposal to try and fix that problem.
Finally, keep in mind that, depending on the alignment, accuracy of your tuning, etc., the output may be falling off and be -6dB already at 18 Hz, since this is below the tuning frequency.
-Charlie
don't underestimate the potential for structural damage to the building from long term exposure to pressures at these levels and frequencies, not to mention possible health issues
not a joke
not a joke
you can actually FEEL the flexing? Dude, more bracing. If you cant, then leave it be. As far as lower freq....thats insane. You will not hear it (as said above) AND the choice of music to actually play those Hz..would be rap I guess. Yucky. Aside from my personal tastes, and please dont take it the wrong way (Im just joking) I think you are at your finality with these speakers. Cheers
wait a min...are you suggesting the walls of your HOME are flexing?????
JESUS RUN FOR YOUR LIFE MAN! seriously.
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Try moving around the room, you may be listening in a place where there is a null, if there is enough acoustic energy to flex the stud walls, you should hear it. The wall flexing is absorbing some LF acoustic energy compared to a solid concrete bunker.
That said, it only takes 5 dB difference to sound twice (or half) as loud at 20 Hz, (compared to 10 dB at 1000 Hz) your sub output level may be just below your hearing perception.
Different ears hear differently. I have no problem hearing 15 Hz in both headphones (which certainly don't provide "body feel") or using the Mackie HRS120 subwoofer in my small control room which can make the stud walls flex and resonate between 15-18 Hz.
Edit: A stud wall has a resonant frequency, it can flex without super high SPL if the tones coincide with the resonant frequency. As has already been pointed out, you box won't put out much SPL below Fb, but it still has enough energy to excite the wall resonance.
Art
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Art - how can you be CERTAIN that what you heard was a 15Hz pure tone??? I really, really doubt it! You probably heard the harmonics (e.g. the distortion) of the transducer, whether it is your headphones or your Mackie subwoofer. I find claims like this very hard to believe, because even small levels of distortion from a transducer supplied with a <30Hz pure tone can dominate the perceived sound because of the ear's relative sensitivity to fundamental (low) and harmonics (higher). But, you ARE right in that everyone's hearing is different, so it is "theoretically possible".
-Charlie
I stuffed a towel in one of the ports. Now tuning is 18Hz (minimal cone excursion). It increased the output. I believe I can hear a pure tone. It doesn't have the impact of say a 30Hz tone, but the walls "pump" and I can feel the vibration coming up through my chair and desk. It even make ripples in the water in the sink.
I'm only powering the sub at 9 volts rms (10 watts) I like sensitive speakers because I use low power amps.
This speaker was more of an experiment. I don't really play any music through it. my tapped horn and another 12" sub are tuned to 30 Hz and that seem plenty low to me.
I have a mental issue called SBS. (Speaker Building Syndrome). Is there a cure?
I'm only powering the sub at 9 volts rms (10 watts) I like sensitive speakers because I use low power amps.
This speaker was more of an experiment. I don't really play any music through it. my tapped horn and another 12" sub are tuned to 30 Hz and that seem plenty low to me.
I have a mental issue called SBS. (Speaker Building Syndrome). Is there a cure?
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With the box tuned to 18Hz you should be able to feel the really low stuff better.
The port and driver are in phase down to the tuning frequency below that the port inversion coupling stops working and the port and the driver are out of phase.
Just for fun I'm going to get a 15Hz tone and see if i can hear it. BRB. 😀
The port and driver are in phase down to the tuning frequency below that the port inversion coupling stops working and the port and the driver are out of phase.
Just for fun I'm going to get a 15Hz tone and see if i can hear it. BRB. 😀
Nope, well I can feel the pressure variations in my ears but mostly I just hear the house flexing.
True, but with the box tuned at 24 Hz, there is extension down to ~15 Hz
This is the sensation I can feel as well. At 18Hz, I hear just a bit. At 15Hz, it is more just a sensation on my eardrums. If you were ever in a van or SUV and rolled a back seat window down and the wind over the window opening started oscillating (Helmholtz resonance) at 5 or 6 Hz, it makes my eardrums tickle. It is kind of like that, but a much smaller sensation.
Isn't the sensation of pressure variations in the ear what is considered hearing? 🙄
I normally don't have any trouble hearing right down to 15 cycles even at fairly low power, certainly well below the point where significant distortion and harmonics would be an issue.
If all you hear are harmonics and distortion products @ 18 cycles, perhaps you need a new subwoofer or four 😉
And yes, even well built walls will "breathe" a little bit, even the ones I just finished building in my new theater room I'm working on. My right side wall was built with the studs firmly pressed into the steel I beam that runs across the ceiling, double footers and screwed to the concrete floor. Even with the volume knob at 8 o'clock a 20 cycle tone can be felt in the wall with your hand as well as heard clear and crisp.
I'm certain the tone was relatively pure, as in under 10% distortion. Having done countless tests measuring distortion, have found LF distortion above 10% to be noticable.
The Sony MDR 7506 headphones have very low distortion at the level I was listening to the tones at.
As another confirmation, 30 or 45 Hz (first and second harmonic of 15Hz) don't make my studio studwalls flap, as they did when "scrubbing" a certain piece of music, the tone and wall reaction was unmistakable ;^).
Originally Posted by weltersys
Edit: A stud wall has a resonant frequency, it can flex without super high SPL if the tones coincide with the resonant frequency. As has already been pointed out, you box won't put out much SPL below Fb, but it still has enough energy to excite the wall resonance.
Art
Edit: A stud wall has a resonant frequency, it can flex without super high SPL if the tones coincide with the resonant frequency. As has already been pointed out, you box won't put out much SPL below Fb, but it still has enough energy to excite the wall resonance.
When the pictures and sound absorbing "cloud" hanging on the wall flop around, the word "flex" rather than "vibrate" seems more descriptive, but that's just a matter of semantics 😀.
Art
You miss the point. Most people (If not all) cant hear 15 hz, so its the THD ( 30 45 60 hz etc ) that they hear. File:Lindos1.svg - Wikipedia, the free encyclopedia
People are at least 30db more sensitive to 45 hz than 15hz. (if they can hear it)
Try concrete or even brick or cinder block.
I'm with cbdb. Do the hearing-math. If you speakers have 10% distortion (or somewhat less), then you are certainly hearing the distortion more audibly than some subsonic note.
Ben
I understand that, it was more tongue-in-cheek I suppose, to suggest that one should just keep throwing driver displacement and amplifier current at it until distortion isn't an issue and the level can be raised to the point where you're either hearing it or struggling to breathe 😀
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